Diabetes mellitus (DM), also known as simply diabetes, is a group of metabolic diseases in which there are high blood sugar levels over a prolonged period. Globally, as of 2013, an estimated 382 million people have diabetes worldwide. In 2012 and 2013 diabetes resulted in 1.5 to 5.1 million deaths per year worldwide, making it the 8th leading cause of death. Novel approaches are required for effective treatment.
Islet transplantation has emerged as a potential therapeutic approach for diabetes and involves the transplantation of isolated islets from a donor pancreas to another person. Once transplanted, the islets begin to produce insulin, actively regulating the level of glucose in the blood. If transplanted cells are not from a genetically identical donor transplant rejection may occur. To prevent this, immunosuppressant drugs are administered, causing a number of unwanted and detrimental side effects. Two critical limitations to islet transplantation are the currently inadequate means for preventing islet rejection, and the limited supply of islets for transplantation. Novel sources of therapeutic cells, in particular autologous cells, are required in order to reduce unwanted side effects and increase efficacy of treatment. One option for the provision of such material is lineage re-programming of non-pancreas cells into pancreas cells.
During embryonic development, cells become gradually restricted in their developmental potential to ultimately acquire a mature differentiated state (reference 1). Seminal work has demonstrated that stable differentiated states can be unlocked and cells can be forced to change their identity either to revert to a pluripotent state or to acquire another differentiated state, a process called lineage reprogramming (references 1, 2, 3). Successful lineage reprogramming relies on the identification of defined factor(s) able to establish the new cell fate transcriptional program and, concomitantly, silence the original gene expression program (references 2, 4, 5, 6).
The references indicated by numerals, for which full citations are provided below under the heading “References” are incorporated herein by reference in their entirety.
Lineage re-programming represents a promising approach for the production of cells for administration in cellular therapy and for the manipulation of cell fate in vivo. Due to the difficulties inherent in obtaining sufficient cell numbers and types for implantation, or in replenishing vital cell types in vivo that may be malfunctioning, re-programming approaches provide advantageous therapeutic means based on novel sources of therapeutic cellular material. The present invention provides tools for manipulating cellular plasticity between liver and pancreas cells, in addition to methods, cells and therapeutic approaches based on the products of fate interconversion between these two cell types.
Evidence of significant plasticity in the adult pancreas has been reported (references 7, 8). In particular, fate interconversion between different pancreatic cell types can occur under extreme beta-cell damage (references 7, 9, 10) or be forced by the expression of pancreatic and/or beta-cell transcription factors (references 8, 11, 12, 13, 14, 15). From a clinical perspective, adult liver cells have some advantages over pancreatic cells, representing a more easily accessible and abundant starting cell population for fate conversion approaches to generate pancreatic cells with therapeutic potentials (references 2, 16). Nevertheless, ectopic expression of pancreatic transcription factors (e.g. Pdx1) in liver appears inadequate, resulting in incomplete phenotypic conversion and hybrid phenotypes (references 16, 17, 18, 19, 20, 21). These observations are consistent with the fact that the two lineages are closely related but yet at a greater distance than cells of the same lineage, e.g. exocrine and endocrine pancreas cells (references 22, 23). Additional limitations might be the lack of appropriate interaction partners or the presence of antagonistic factors in liver cells that lock cell identity, hampering cell plasticity and conversion.
To overcome these lineage restrictions, the present invention is based on the use of regulator(s) of the pancreas versus liver fate decision that act upstream of Pdx1 in the specification cascade, thereby providing effective reprogramming determinants for achieving full conversion of liver cells into pancreas cells of therapeutic relevance.